You've got the vision. You're building something people want. You're probably running on a mix of adrenaline, a Notion doc, and a Revolut business account.

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The last thing on your mind is your finance function.

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And honestly? That's fine...for a while.

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But here's the thing: more Series A rounds fall apart, stall, or come back with painful terms because of avoidable finance problems than most founders ever realise. Not bad ideas. Not bad products. Bad financials.

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After working with dozens of early-stage startups, the same five mistakes come up again and again. Here's what they are, and how to get ahead of them.

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Mistake #1: Treating Your Accountant Like a CFO

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Your accountant is brilliant. They file your accounts, keep HMRC happy, and make sure you're not accidentally committing fraud. But they are not your strategic finance partner.

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A CFO-level thinker is asking 'bigger picture' questions:

• What does our burn rate tell us about our next 18 months?
• Are we pricing our product in a way that actually supports the business we want to build?
• What does our unit economics story look like to an investor?

If nobody in your business is asking those questions right now, that's the gap.

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The fix? You don't need a full-time CFO at pre-seed or seed. You need someone who thinks like one, a few days a month. That's exactly why fractional finance exists.

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Mistake #2: No Financial Model (Or One Nobody Believes)

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Every founder has a spreadsheet. Most of them are...let's just say, very optimistic.

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That's not a criticism; founders are supposed to be optimistic. But investors have seen thousands of financial models, and they can spot a 'top-down hockey stick' from a mile away.

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What actually impresses investors at Series A is a bottoms-up model: one that starts from real assumptions about customer acquisition, conversion, and churn, and builds up to revenue from there. It shows you understand your business mechanically, not just aspirationally.

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The best financial model doesn't predict the future. It shows that you understand the levers that drive your business.

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Build it early, stress-test it often, and make sure it tells a coherent story alongside your pitch deck.

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Mistake #3: Losing Track of Cash Until It's Nearly Gone

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Runway awareness is probably the most critical financial skill for any early-stage founder. And yet it's surprisingly common for founders to discover they have 6–8 weeks of runway left without having planned for it.

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For any early stage company, cash is always king.

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The problem is rarely negligence. It's that founders are building, selling, hiring, and firefighting all at once. Finance slips to the background until it can't.

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What you need is a simple, rolling cash flow forecast. Not complicated. Not a full finance transformation. Just a clear view of what's coming in, what's going out, and when the pinch points are.

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With that visibility, you make proactive decisions. Without it, you make panic decisions.

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Mistake #4: Messy Cap Table and Equity Conversations

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This one is painful to watch.

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Founders who gave away too much equity too early. Advisors with outsized stakes who haven't added value in two years. Co-founders with no vesting schedule. Early angels with unusual rights baked in.

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None of these are fatal on their own but combined, they can make your company genuinely difficult to invest in.

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Series A investors do serious cap table diligence, and a messy structure raises red flags about governance and future fundraising.

• Use a proper cap table tool from day one (Carta, Capdesk, Seedlegals), there are good options for every stage.
• Make sure every equity grant has a vesting schedule.
• Get clean legal advice before you issue shares, not after.

Sort this early. It's much cheaper and less painful to fix before you're in a fundraise.

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Mistake #5: Not Knowing Your Key Metrics Cold

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Picture this: you're in a Series A meeting. An investor asks, 'What's your LTV:CAC ratio?' and you say, 'We're still working on how to calculate that.'

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That's a moment you really don't want.

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By the time you're approaching Series A, you should know your key metrics instinctively, and more importantly, you should be able to explain what's driving them and what you're doing to improve them.

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For most B2B SaaS businesses, this means:

• MRR and MRR growth rate
• Churn rate (logo and revenue)
• LTV:CAC ratio
• Average contract value and sales cycle length
• Gross margin

For B2C or marketplace businesses, the specific metrics differ. But the principle doesn't. Know your numbers. Own them, and be confident enough to defend them when called upon.‍

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So, Where Do You Start?

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‍None of these mistakes require a finance degree to fix. They require time, clarity and, at the right moment, the right finance partner alongside you.

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The honest truth is that most early-stage founders don't need a full-time CFO. They need someone who can:

• Build and own a financial model that investors actually believe
• Give them real visibility on cash and runway
• Prepare them for the financial due diligence of a raise
• Be a sounding board on pricing, hiring decisions, and growth trade-offs

That's the fractional finance model. Senior-level thinking, without the senior-level overhead.

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If any of the five mistakes above made you think 'that's us right now' - let's have a conversation. No pressure, just a chat about where you are and whether we can help.

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